1. Field of the Invention
The present invention relates to an optical sheet. More particularly, the present invention relates to an optical sheet simultaneously having a refractive function and a reflective function.
2. Description of Related Art
With development of technology, display devices are widely used in people's daily life, in which flat panel displays (FPDs) become popular due to its features of light-weight and thin-size. In various FPDs, liquid crystal displays (LCDs) are widely used due to its advantages of high space usage rate, low power consumption, no radiation and low electromagnetic interference, etc.
FIG. 1 is a cross-sectional view of a conventional LCD. Referring to FIG. 1, the LCD 100 includes a liquid crystal panel 110 and a backlight source 120, wherein the backlight source 120 is used for providing an incident light L to the liquid crystal panel 110. In detail, the liquid crystal panel 110 generally includes an upper polarizer 110a, an upper substrate 110b, a liquid crystal layer 110c, a lower substrate 110d and a lower polarizer 110e. After the light L provided by the backlight source 120 enters the liquid crystal panel, the lower polarizer 110d polarizes the light L emitted from the backlight source 120 into a polarized light LT. Based on different rotations of liquid crystal molecules in the liquid crystal layer 110c, transmissivities of the polarized light LT in different regions can be varied. Then, the polarized light LT is emitted from the upper polarizer 110a. By such means, the liquid crystal panel 110 can achieve a display effect.
Though the upper polarizer 110a and the lower polarizer 110e can polarize the light L to assist an optical effect of an image displayed by the LCD 100, the light L may have a loss when passing through the upper polarizer 110a and the lower polarizer 110e, so that the light L emitted form the backlight source 120 may have an energy depletion within the LCD 100, and accordingly a brightness performance of the LCD 100 is influenced. Generally, the upper polarizer 110a and the lower polarizer 110e are applications of optical sheets. Therefore, how to suitably design a structure of the optical sheet to improve a light usage rate of the LCD 100 is a major challenge required to be ocvercomed for the FPDs.